Field of the Invention
The present invention relates to a pneumatic tire in which a projection for suppressing stone sticking is formed.
Background Art
There is a pneumatic tire (hereinafter, referred to as “tire”) including a projection (called “stone ejector”) for suppressing stone sticking, that is, sticking of small stones in a groove formed in the tread. For example, a tire disclosed in JP H10-100616 A can be mentioned.
The projection of the tire disclosed in JP H10-100616 A is a projection having a triangular prism shape projecting from a groove bottom. Small stones that have entered the groove in which the projection is formed during running of the tire are prevented from entering the inside of the groove by abutting the top surface of the projection. Further, this projection has a triangular cross sectional shape, and therefore the rigidity on the top side in the triangle is lower than the rigidity on the bottom side of the triangle. Accordingly, in the case where small stones enter the groove and press the upper part of the projection, the deformation amount on the top side of this projection is relatively large. In this way, the deformation amount of the projection is different depending on the parts. Therefore, the tread contacts the ground, and the projection swings every time the upper part of the projection is pressed by small stones, which allows the small stones to be ejected from the groove by moving them toward the direction in which the projection easily deforms in the groove.
However, once small stones are stuck between a side of the groove and a side of the projection, the projection having a triangular prism shape is difficult to swing, since the thus stuck small stones do not press the upper part of the projection. Therefore, the stuck small stones are difficult to move in the groove, and may remain stuck without being ejected from the groove in some cases. The small stones remaining stuck in the groove as above are not preferable because the small stones cause damage to the tread such as cracks in blocks by pressing the blocks.